What the Hex Going On at Saturn's Pole?

When it comes to where the atmospheric action is in the outer planets, move over Jupiter. As if having those gaudy rings weren't enough, Saturn is definitely hogging all the attention by sporting some bizarre atmospheric activity at opposite ends of the planet: polar storms, one with a cyclopean eye and the other shaped like a—hexagon.

This wonderfully weird hexagonal storm recently photographed by Cassini wheeling around Saturn's north pole is not an ephemeral phenomenon, one of those lucky, photo-opportune moments in which a dynamic event happened to take on a distinct, precise shape that can only be coincidental. Rather, the six-sided maelstrom was first imaged in 1980 by both Voyager spacecraft—and that's the thing about it: it's still there. Storms are not supposed to have straight sides and sharp angles—at least not here on Earth. I suppose that is the joy of expanding our scientific horizons with all this space exploration stuff.

It is still too soon to know if this enigmatic feature in the Saturnian atmosphere will have the durability of Jupiter's Great Red Spot, which has been watched by astronomers for over 400 years. But for this strange feature to endure for even a quarter of a century, there must be some dynamic physical processes at work that remain to be discovered. But in wondering just what this thing is, I am in good company. JPL atmospheric expert and Cassini visual and infrared mapping spectrometer team member Kevin Baines had this to say about it:

"This is a very strange feature, lying in a precise geometric fashion with six nearly equally straight sides. We've never seen anything like this on any other planet. Indeed, Saturn's thick atmosphere where circularly-shaped waves and convective cells dominate is perhaps the last place you'd expect to see such a six-sided geometric figure, yet there it is."

Keeping in mind Richard Dawkin's observation that the universe does not owe us meaning, seeing this atmospheric oddity conjures up other phenomena in the solar system and on Earth that coincidentally take on precise shapes and forms we normally consider of only anthropomorphic origin. So many objects and features in Earth and sky are named for everyday structures, like, for instance, the ring or dumbbell nebulae. But although gas blowing out of a supernova in the shape of a ring or fan stimulates the imagination, it flatters, rather than challenges our view of just what we can create and what a gas cloud cannot. We chalk up to coincidence objects like the Horsehead and Cat's Eye nebulae. It's like looking at clouds on a lazy summer day and trying to glean objects out of their ever-shifting shapes. We're doing that when we look at the cosmos, too, but the gas clouds that we see give us a long time (eons) to share and enjoy their current, though hardly permanent coincidental shapes. It happens on Earth, too: for instance, the shape of the Italian peninsula—in this geologic moment, really does resemble a boot. And there is the ageless "man in the moon" based on the position of lighter highlands and darker maria, or the Viking 1 orbiter's "face on Mars" image. Some impressions, like the latter, rely on poor camera resolution and a human need to find something where it isn't, whereas others, like the moon's "face," on the same healthy human imagination that brought us the constellations.

But this hexagonal storm thing…. A hexagon? Formed by atmospheric circulation? I guess it would even be even more improbable if it was longitudinally moving around the planet like Jupiter's Red Spot. But it still seems too geometrical to be a storm or circulation. If it was a hex-shaped crater on Mars, I could accept it with less puzzlement. Look at Saturn's other pole. The hurricanelike swirl—similar to Earth's polar circulation and complete with a reassuring, though eerie, vortical eye—is a little more comforting for me from my provincial Earth-centric reference point to accept.

Over the intervening years since Voyager's initial discovery of the Hex, scientists have puzzled over what this atmospheric feature is. Since the feature—about four times the size of Earth, around 15,000 miles (25,000 kilometers) across, and extending 60 miles (100 kilometers) below the cloud tops—was discovered, some planetary scientists have speculated that it is a stationary Rossby wave. Others theorized that the storm might somehow tied to Saturn's radio emissions or polar auroral activity, but with the new imagery and data, these explanations are no longer favored.

As Cassini makes more passes over the Saturnian north pole in the next two years, the region will be emerging from its seven-year winter; more images and data might help perplexed scientists figure out the processes behind this uniquely shaped oddity. But that's not guaranteed. When all the data from Cassini is in, it may remain a enigma that begs further exploration in the coming decades.

If this feature proves to be durable, it will be fascinating to watch as researchers develop theories. Not only will it make the solar system an even stranger place, it may even help them find the answer to another of the sixth planet from the sun's mysteries—its rotation rate.

Meanwhile, it will be fun to hear will be all the conspiracy theories about it that will emerge—move over "face on Mars." I can't wait to read about the extraterrestrial machinations hexing Saturn in line at the supermarket. Perhaps the explorers in 2001 A Space Odyssey went to the wrong gas giant: You see, if you take monoliths and overlap them correctly, you can create a hexagon…. And just imagine if it was a pentagon that was discovered on Saturn.

You have already sent in some interesting ideas to JR Minkle's March 28 post. Keep 'em coming. All scientific, pseudoscientific or conspiratorial theories as well as extraterrestrial extrapolations are welcome. We all might as well have a little fun until the planetary scientists at JPL come up with an explanation based on either good old-fashioned classical physics, or maybe something that even beats our wildest ruminations.

Image Credit: NASA/JPL/University of Arizona

The views expressed are those of the author and are not necessarily those of Scientific American.

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